1. Field of the Invention
The present invention relates generally to transmissions and, more particularly, to a synchronizer mechanism for synchronizing rotation of gears in a manual transmission.
2. Description of the Related Art
Drive linkages are employed in automotive vehicles between the prime mover, typically an internal combustion engine, and the driven wheels. Such drive linkages generally include a line of rotating components from the rotating output of the engine to the rotating input to the driven wheels. A transmission is typically employed in order to vary the ratio of speeds between the engine output and the driven wheel input. The transmission is shifted to give the operating speeds or power ratios required. A clutch, torque converter or fluid coupling is also employed for interrupting power transmission between the engine output and the driven wheels.
A manual transmission typically includes two shafts, one forming the input shaft to which power is applied and the other forming the output shaft which is ultimately connected, usually through a differential mechanism, to the driven wheels. In its most common form, at least two pair of mated gears are mounted respectively on the input and output shafts, and the respective pair of gears are continuously engaged with one another. One gear of each pair is keyed non-rotatably to its respective shaft while the other is freely rotatable on its respective shaft. Thus, although the gears are continually meshed, with nothing more, rotation of the input power shaft does nothing to cause rotation of the output shaft.
In order to selectively key the rotatably mounted gear to its respective shaft, a gear clutch or synchronizer is located adjacent the gear. A synchronizer mechanism is one common form of such a gear clutch. Synchronizer mechanisms are small clutches maintained engaged by the change-speed control during the time required to obtain the equalization of the angular speeds of the elements to be clutched, e.g., the adjacent gears. In such synchronizer mechanisms, a synchronizer sleeve is disposed about a hub fixed to a shaft. The sleeve is moveable axially relative to the hub on the shaft and into or out of engagement with the adjacent gear. A shifting linkage is manually activated to provide this axial shifting. Cooperating teeth on the coupling member and gear are then engaged in the drive position to key the gear via the coupling member to the shaft. The teeth must be synchronized before shifting can take place and often a main clutch is needed to accomplish this and to interrupt torque transmission through the gear set.
It is not uncommon to encounter excessive play in the movement of the synchronizer sleeve with respect to the hub over many shift iterations. This deficiency is manifested in excessive hub to sleeve tilting which can ultimately result in excessive shift system play causing a popping out of gear condition. In addition, shift system inertial effects can cause jumpout during torque reversals between the gear clutch teeth and synchronizer sleeve.